ILLUSTRATIONS (18). CLIMATE OF AMERICA. 103 



north lat.), the mean annual winter temperature is only half a 

 decree below the freezing-point, whilst, at a distance from the 

 lakes, in 4-i 53' north lat. at Fort Snelling. near the conflu- 

 ence of the river St. Peter with the Mi>M>Mppi. the mean 

 winter temperature is 16. 8 Fuhr.* At this di.Mance from the 

 Canadian lakes, whose surface is from rive to upwards of MX 

 hundred feet above the sea's level, whilst the bottom of 

 Lakes Michigan and Huron is five hundred feet below it, 

 recent observations have shown that the climate of the country 

 possesses the actual continental character of hotter summers 

 and colder winters. "It is proved," says Forry, "by our 

 thermometrical data, that the climate west of the Alleghany 

 chain is more excessive than that on the Atlantic side." At 

 Fort Gibson, on the Arkansas river, which falls into the Mis- 

 sissippi, in lat. 35 47', where the mean annual temperature 

 hardly equals that of Gibraltar, the thermometer was observed, 

 in August, 1834, to rise to 117 Fahr. when in the shade, 

 and without any reflected heat from the ground. 



The statements so frequently advanced, although unsup- 

 ported by measurements, that since the first European settle- 

 ments in New England, Pennsylvania, and Virginia, the de- 

 struction of many forests on both sides of the Alleghanyt, has 

 rendered the climate more equable, making the winters milder 

 and the summers cooler, are now generally discredited. 

 No series of thermometric observations worthy of confidence 

 extend further back in the United States than seventy-eight 

 years. We find from the Philadelphia observations that from 

 1771 to 1824, the mean annual heat has hardly risen 2. 7 

 Fahr.; an increase that may fairly be ascribed to the exten- 

 sion of the town, its greater population, and to the numerous 

 st cam-engines. This annual increase of temperature may also 

 be owing to accident, for in the same period I find that there 

 was an increase of the mean winter temperature of 2 Fahr. ; 

 but with this exception the seasons had all become somewhat 

 warmer. Thirty-three years' observations at Salem in Massa- 

 chusetts show scarcely any difference, the mean of each one 

 oscillating within 1 of Fahrenheit, about the mean of the 

 whole number; and the winters of Salem, instead of having 

 been rendered more mild, as conjectured, from the eradication 



* See the admirable treatise by Samuel Forry, on The Climate of 

 the United States, 1842, pp. 37, 39, 1U 



